[SampleFDO] Fix -Wnon-virtual-dtor

Make the dtor virtual to fix the warning.

Author: xur-llvm

llvm/include/llvm/Transforms/Utils/SampleProfileLoaderBaseImpl.h

@@ -114,7 +114,7 @@ template <typename BT> class SampleProfileLoaderBaseImpl {
       DenseMap<const BasicBlockT *, SmallVector<const BasicBlockT *, 8>>;
 
 protected:
-  ~SampleProfileLoaderBaseImpl() = default;
+  virtual ~SampleProfileLoaderBaseImpl() = default;
   friend class SampleCoverageTracker;
 
   Function &getFunction(FunctionT &F) {